This invention relates to an improvement in a copier capable of varying its image magnification ratio by moving an optical system such as a lens.
An electrophotographic copier is provided with an optical system including a light source, mirrors and a lens to focus a beam of light reflected from an original document to be copied on a photosensitive body to form thereon a latent image. The magnification of the image thus formed by an optical system on the photosensitive body is usually 100% with respect to the original document but the image magnification can be varied by moving the optical system. With a conventional copier, copying with a different magnification ratio is usually effected by key-inputting a desired magnification ratio so as to cause the optical system to move according to the inputted ratio and thereafter operating a print switch to make a copy at the desired magnification ratio. If the user of a conventional copier thus structured changes the setting several times before finally operating the print switch, however, the optical system is moved to a new position as many times and this causes the optical system to wear out quickly.
Some copiers are provided with an auto-clear function such that most frequently used magnification ratio and concentration are set as a default mode and if a preset length of time passes without any key-input, the default mode of operation is automatically set. If the user of such a copier enters a desired magnification ratio and leaves the area momentarily, however, the optical system which has once moved to the position corresponding to the desired magnification ratio returns to its original position corresponding to its default mode. This means that the desired magnification ratio must be inputted again and the optical system must accordingly be moved again. To cause the optical system to make many useless trips is also to waste the operation time.